Method and system for evaluating optical properties of compensation layer

Abstract

A compensation layer optical property evaluation method capable of precisely and accurately evaluating the optical properties of the compensation layer without separating the compensation layer from the optical film, namely without causing a breakage of the compensation layer or a change in the optical properties, and to provide a compensation layer optical property evaluation system for use in such a method. The method for evaluating the optical properties of a compensation layer in an optical film comprising at least a polarizer and the compensation layer placed thereon, comprising the steps of: preparing the optical property data that represent the relationship between the ellipticity of polarized light and optical properties of the compensation layer, wherein the optical properties include front retardation R 0 , thickness retardation R th , bonding angle θ, and average tilt angle β; measuring the ellipticity of polarized light through a sample of the optical film,; extracting the optical property data equal or close to the measured ellipticity of the polarized light from the data prepared in the data preparing step.

1 . A method for evaluating the optical properties of a compensation layer in an optical film comprising at least a polarizer and the compensation layer placed thereon, comprising the steps of:
 preparing the optical property data that represent the relationship between the ellipticity of polarized light and optical properties of the compensation layer, wherein the optical properties include front retardation R 0 , thickness retardation R th , bonding angle θ, and average tilt angle β;   measuring the ellipticity of polarized light through a sample of the optical film,;   extracting the optical property data equal or close to the measured ellipticity of the polarized light from the data prepared in the data preparing step,   wherein the ellipticity measuring step, natural light is applied to a polarizer side surface of the optical film at a given angle with respect to a horizontal surface of the optical film, and the optical film is rotated about a vertical axis of the horizontal surface of the optical film, when the ellipticity of the polarized light is measured.   
   
   
       2 . The method of  claim 1 , wherein the optical property data preparing step further comprises the step of theoretically calculating data representing the relationship between the ellipticity of polarized light and the optical properties including front retardation R 0 , thickness retardation R th , bonding angle θ, and average tilt angle β. 
   
   
       3 . The method of  claim 1 , wherein the optical property data preparing step further comprises the step of measuring, by measurement means, data representing the relationship between the ellipticity of polarized light and the optical properties including front retardation R D , thickness retardation R th , bonding angle θ, and average tilt angle β. 
   
   
       4 . The method of  claim 1 , wherein the optical property data preparing step further comprises the steps of:
 theoretically calculating data representing the relationship between the ellipticity of polarized light and the optical properties including front retardation R 0 , thickness retardation R th , bonding angle θ, and average tilt angle β;   measuring, by measurement means, data representing the relationship between the ellipticity of polarized light and the optical properties including front retardation R 0 , thickness retardation R th , bonding angle θ, and average tilt angle β; and   correcting the calculated data so that the calculated data can be an approximation to the measured data.   
   
   
       5 . The method of  claim 1 , wherein in the optical property data extracting step, when four peak ellipticity values measured in the ellipticity measuring step are the same, a data equal or close to the peak value is extracted from the data prepared in the data preparing step so that the front retardation R 0 , thickness retardation R th , and average tilt angle β at a bonding angle θ of 0° can be determined. 
   
   
       6 . The method of  claim 1 , wherein in the optical property data extracting step, when four peak ellipticity values measured in the ellipticity measuring step are not the same, the average of the peak values is calculated, and a data equal or close to the calculated average peak value is extracted from the data prepared in the data preparing step so that the front retardation R 0 , thickness retardation R th , and average tilt angle β can be determined. 
   
   
       7 . The method of  claim 6 , wherein the difference between the calculated average peak value and a maximum or minimum peak value is calculated, and a data equal or close to the calculated difference is extracted from data on peak ellipticity versus bonding angle θ shift prepared in the data preparing step so that the bonding angle θ indicating axis misalignment in a bonding process can be determined 
   
   
       8 . The method of  claim 1 , wherein
 the ellipticity measuring step comprises applying natural light to a polarizer side surface of the optical film at two different angles with respect to the horizontal surface of the optical film to measure the ellipticities of two types of polarized light, and   the optical property data extracting step comprises extracting a data equal or close to each of the measured ellipticities of the two types of polarized light from the data prepared in the data preparing step.   
   
   
       9 . The method of  claim 1 , wherein
 the ellipticity measuring step comprises using natural light with two different wavelengths to measure the ellipticities of two types of polarized light, and   the data extracting step comprises extracting a data equal or close to each of the measured ellipticities of the two types of polarized light from the data prepared in the data preparing step.   
   
   
       10 . The method of  claim 1 , wherein the compensation layer satisfies the relation nx>ny>nz, wherein nx is its refractive index in its slow axis direction, ny is its refractive index in its fast axis direction, and nz is its refractive index in its thickness direction. 
   
   
       11 . A system for evaluating the optical properties of a compensation layer in an optical film comprising at least a polarizer and the compensation layer placed thereon, comprising:
 an optical property data storage unit for storing data that represent the relationship between the ellipticity of polarized light and optical properties of the compensation layer, wherein the optical properties include front retardation R 0 , thickness retardation R th , bonding angle θ, and average tilt angle β;   an ellipticity measurement device for measuring the ellipticity of polarized light through a sample of the optical film;   an optical property data extraction unit for extracting a data equal or close to the measured ellipticity of the polarized light from the data stored in the optical property data storage unit,   wherein measuring by the ellipticity measurement device, natural light is applied to a polarizer side surface of the optical film at a given angle with respect to a horizontal surface of the optical film, and the optical film is rotated about a vertical axis of the horizontal surface of the optical film, when the ellipticity of the polarized light is measured.